In a radio communication system, fading involved in movement mainly deteriorates radio communication quality. As a method of reducing the quality deterioration due to the fading, there is known a space-time coded transmission diversity system for arranging a plurality of antennas in a terminal or a base station to reduce a correlation of propagation path fluctuation of each of the antennas and suppressing a decrease in electric power due to fading making use of the difference in the propagation path fluctuation among the antennas. Patent literature 1 discloses a differential space-time coded transmission diversity in which coding based on differential coding, capable of following high-speed propagation path fluctuation compared with a synchronous detection system, is adapted to space-time coding by generating a symbol using, as a change amount on a phase space, transmission information corresponding to transmission bits among continuous symbols. In a radio communication system that performs synchronous detection according to a transmission line estimation result at a frame head, when a long-term frame is used, high oscillator accuracy or high frequency correction accuracy is requested. In the differential coding, information to be transmitted is present in the change amount on the phase space. Therefore, when the differential coding is applied, it is possible to relax oscillator accuracy or frequency correction accuracy.